The present invention relates to an inspection apparatus for a conductive pattern of a circuit board and to a sensor for the inspection apparatus.
In manufacturing processes of a circuit board, after forming an electrically conductive pattern on a board, it is required to inspect the presence of disconnection and/or short-circuit in the conductive pattern.
As for such an inspection technique, a contact type inspection technique has been heretofore known in which a conductive pattern was subjected to a continuity check or the like by bringing two separate pins into contact with the opposed ends of the conductive pattern to apply an electric signal from one of the two pins to the conductive pattern ant then receive the electric signal through the other pin.
However, recent progressive densification in the conductive pattern makes it difficult to assure a sufficient space for arranging the pins simultaneously and bringing them into contact with the conductive pattern to be inspected. Thus, a non-contact type inspection method has been proposed in which the electric signal was received without using any pin and contacting the conductive pattern (see Japanese patent Laid-Open publication No. Hei. 09-264919).
As shown in FIG. 15, in this non-contact type inspection technique, the disconnection or the like in the conductive pattern is inspected by bringing a pin into contact with one of the ends of a circuit wiring of the conductive pattern to be inspected, placing a sensor conductor at the other end of the conductive pattern in a non-contact manner, and then detecting with the sensor conductor a potential variation in the conductive pattern caused by supplying an inspection signal to the pin. This arrangement may be represented by an equivalent circuit as shown in FIG. 16, in which a current generated on the sensor conductor is amplified by an amplifier circuit, and then the disconnection and short-circuit of the conductive pattern at a position opposed to the sensor conductor is detected based on the magnitude of the amplified current.
In the above conventional non-contact inspection technique, an electromagnetic wave from the conductive pattern has been received by an electrode having a size to substantially cover over a plurality of pattern lines on a standard circuit board. Thus, it has been impossible to inspect the circuit pattern in the level of 50 xcexcm with a high degree of resolution. Further, even in a relatively large conductive pattern, it has not been able to go so far as detecting a chipping therein.
The present invention has been embodied to solve the above problems in the prior arts. It is therefore an object of the present invention to provide a sensor and inspection apparatus capable of inspecting the shape or geometry of the conductive pattern precisely.
In order to achieve the above object, according to a first aspect of the present invention, there is provided an inspection apparatus for inspecting a conductive pattern of a circuit board, in which a potential variation caused by applying an inspection signal to the conductive pattern is detected in a non-contact manner, which comprises detect means for detecting the potential variation in each portion of the conductive pattern by use of a plurality of sensor elements; and select means for outputting a select signal for selecting the sensor elements, wherein each of the sensor elements is formed either on a single-crystal of a semiconductor or on a flat plate, and each of the sensor elements includes a passive element operable as a counter electrode coupled capacitively with the conductive pattern to detect the potential variation in the conductive pattern, and a transistor adapted to output a detect signal in response to the select signal which is input into the transistor, the detect signal being output from the passive element.
The transistor may be a current-readout MOSFET. In this case, the passive element is continuously formed with a diffusion layer served as a source of the MOSFET to be electrically conductive thereto, and the detect signal is obtained from a drain of the MOSFET by inputting the select signal into a gate of the MOSFET.
The transistor may otherwise be a current-readout thin-film transistor. In this case, the passive element is connected to a source of the thin-film transistor, and the detect signal is obtained from a drain of the thin-film transistor by inputting the select signal into a gate of the thin-film transistor.
The transistor may otherwise be first and second MOSFETs connected in series with each other. In this case, the passive element is connected to a gate of the first MOSFET, and the select signal is connected to a gate of the second MOSFET. Further, a potential at a source of the first MOSFET is varied in response to the potential at the passive element applied to the gate of the first MOSFET, the varied potential being received by a drain of the second MOSFET, and the received potential being output from a source of the second MOSFET as the detect signal.
The transistor may otherwise be first and second thin-film transistors connected in series with each other. In this case, the passive element is connected to a gate of the first thin-film transistor, and the select signal is input to a gate of the second thin-film transistor. Further, a potential at a source of the first thin-film transistor is varied in response to the potential at the passive element applied to the gate of the first thin-film transistor, the varied potential being received by a drain of the second thin-film transistor, and the received potential being output from a source of the second thin-film transistor as the detect signal.
The transistor may otherwise be a bipolar transistor. In this case, the passive element is connected to an emitter of the bipolar transistor, and the detect signal is obtained from a collector of the bipolar transistor by inputting the select signal to a base of the bipolar transistor.
The transistor may otherwise be a charge-readout MOSFET. In this case, the passive element is formed continuously with a diffusion layer serving as a gate of the MOSFET to be electrically conductive thereto. Further, a potential barrier formed below the gate is lowered by inputting the select signal into the gate of the MOSFET, a signal charge residing in a source of the MOSFET being transferred to a drain of the MOSFET as a charge for the detect signal, and the detect signal being transferred by a charge-transfer element connected to the drain of the MOSFET.
In the above case, a charge-supply MOSFET for supplying a charge to the passive element in response to the potential variation in the conductive pattern and forming a potential barrier not to cause the backflow of the supplied charge before completing the potential variation in the conductive pattern may further be included. The charge-supply MOSFET may have a drain formed continuously with the diffusion layer serving as the passive element to be electrically conductive thereto.
The sensor elements according to the first aspect of the present invention may be arranged on a sensor chip in a matrix form.
The inspection apparatus according to the first aspect of the present invention may further include a conductor plate contacting the surface of the passive element.
According to a second aspect of the present invention, there is provided an inspection apparatus for inspecting a conductive pattern of a circuit board, which comprises supply means for supplying an temporally varied inspection signal to the conductive pattern; detect means for detecting a potential variation, corresponding to the inspection signal, in each portion of the conductive pattern by use of a plurality of sensor elements; and select means for outputting a select signal for selecting the sensor elements, wherein each of the sensor elements is formed on a single-crystal of a semiconductor, and each of the sensor elements includes a passive element operable as a counter electrode coupled capacitively with the conductive pattern to detect the potential variation of the conductive patter, and a transistor adapted to output a detect signal in response to the select signal which is input into the transistor, the detect signal being output from the passive element.
According to a third aspect of the present invention, there is provided an inspection apparatus for inspecting a conductive pattern of a circuit board, which comprises supply means for supplying an temporally varied inspection signal to the conductive pattern; detect means for detecting a potential variation, caused by supplying the inspection signal, in each portion of the conductive pattern by use of a plurality of sensor elements to output a detect signal corresponding to the potential variation; and select means for outputting a select signal for selecting the sensor elements, image data generating means for generating image data for representing a shape of the conductive pattern based on the detect signal, wherein each of the sensor elements is formed on a single-crystal of a semiconductor, and each of the sensor elements includes a passive element operable as a counter electrode coupled capacitively with the conductive pattern to detect the potential variation of the conductive patter, and a transistor adapted to output the detect signal in response to the select signal which is input into the transistor, the detect signal corresponding to the potential variation detected by the passive element.
The inspection apparatus according to the first to third aspect of the present invention may further include shading means for preventing light from irradiating the semiconductor serving as the sensor elements.
According to a fourth aspect of the present invention, there is provided a sensor for inspecting a conductive pattern of a circuit board, comprising a plurality of sensor elements for detecting a potential variation caused by supplying an inspection signal to the conductive pattern, in a non-contact manner, wherein each of the sensor elements is formed on a single-crystal of a semiconductor, and each of the sensor elements includes a passive element operable as a counter electrode coupled capacitively with the conductive pattern to detect the potential variation in the conductive pattern, and a transistor adapted to output a detect signal in response to the select signal which is input into the transistor, the detect signal being output from the passive element.